{  Statement: http://acmp.ru/?main=task&id_task=46
   Verdict: Accepted
}
uses
    SysUtils, Math;

const
    e:double = 2.7182818284590452353602875;

var
    n:longint;

begin
reset(input,'input.txt');
rewrite(output,'output.txt');
read(n);
if n < 16 then write(e:0:n) else
if n = 16 then write('2.7182818284590452') else
if n = 17 then write('2.71828182845904524') else
if n = 18 then write('2.718281828459045235') else
if n = 19 then write('2.7182818284590452354') else
if n = 20 then write('2.71828182845904523536') else
if n = 21 then write('2.718281828459045235360') else
if n = 22 then write('2.7182818284590452353603') else
if n = 23 then write('2.71828182845904523536029') else
if n = 24 then write('2.718281828459045235360288') else
if n = 25 then write('2.7182818284590452353602875');
end.